How to test a serial port using Windows hyperterminal.

This tutorial applies to a computer running Microsoft windows, and relies on the built in terminal program Hyperterm. If your installation of Windows does not have the program, you may have to install it by using the control panel add/remove programs function. The instructions below were written using a Windows 2000 system, so some of the details may be slightly different for your version of windows and the accompanying Hyperterminal program. You may want to print these instructions so you will have them handy while you are working.

You will need a method of looping back the serial port signal. One way to do this is to obtain a 9 pin D connector (female) which will plug into the serial port. Radio shack part number 276-1538 is suitable, but similar connectors are available at most electronic parts supply stores. Construct a test socket by wiring pins 2 and 3 together with a short length of wire. Take care to connect to the correct pins (they are usually numbered on the connector) and do not connect or short to any other pins. You can solder the jumper wire in place, or you may be able to use a test lead with micro clips at each end. Leave all remaining pins unconnected. Have this test socket handy for use in the following steps.

Serial port Loopback test
1. Boot your computer. After Windows loads, be sure to close any programs that may be running automatically to ensure they do not interfere with the tests.

2. Run the Hyperterminal program. The usual method is: Click START/PROGRAMS/ACCESSORIES/COMMUNICATIONS/HYPERTERMINAL

3. 'New Connection' dialog window will pop up. Enter a name for the connection session. You can choose any name you wish, such as TESTPORT. Click OK.

4. 'Connect To' dialog window will pop up. Ignore the data boxes for phone or dialing information. On the drop down box, select the com port that you will be testing. In this example COM1. Be sure you select the correct COM port, because it is the only port that will be tested unless you repeat the test proceedure for each port to be checked. Click OK.
Note: If you don't see the desired com port in the dropdown list, it means the operating system does not see the port. The port may be defective, disabled, in use, or the port drivers may not be installed correctly.

5. 'Port Setting' dialog window will pop up. Select the settings in each drop down box as follows:
Bits per second 19200
Data bits 8
Stop bits 1
Flow control NONE
When you have adjusted the settings, click OK.

6. Hyperterminal main window will be displayed.
Click in the text window, then type in a few characters. You should not see the characters that you type.
If you see characters, the local echo is turned on and it should be off. To turn it off, click FILE / PROPERTIES, then click the SETTINGS tab. Click the ASCII SETUP button, and uncheck the ECHO TYPED CHARACTERS LOCALLY box.

7. Plug the test connector socket into the Com port to be tested.
Be sure to find the correct physical port which corresponds to the port you selected in step 4, because this is the only port which will be tested.
Click in the main hyperterminal window, then type in a few characters. You should now see the message that you typed. Since it is actually the returned message which was looped back through the test connector, it indicates that the port is able to transmit and receive. If you still see no characters, some aspect of the port is not working correctly.

When you exit hyperterminal there is no need to save the connection file. You can repeat the test for any other COM ports you need to test.

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